There is known a storage device (cf. S. Hassoni, Microprogrammnoye upravleniye (Microprogram Control), Series II Moscow, 1974, pp.127-129), comprising a memory unit for storing control information, to whose output there is connected a constant register connected to a functional return address jump register; a next address register electrically coupled to the memory unit for storing control information; an analysis code register connected to an analysis signal forming decoder; an instruction unit whose output is electrically coupled to the memory unit for storing control information; and main coincidence circuits electrically coupled to the analysis signal forming decoder and the memory unit for storing control information. The number of analysis code registers is equal to the number of address digits being modified of the memory unit for storing control information, and the number of analysis signal forming decoders is equal to that of the analysis code registers.
The necessity of having an individual analysis code register for each modifying address digit of the memory unit for storing control information limits the number of modifiable address digits, since an increase in their number leads to an increase in the number of analysis code registers. This dependence and the limitation it entails affect the relationship between the digit capacity of the analysis code registers and that of the memory unit for storing control information, which means that they reduce the storage capacity of the memory unit to be used to control an object.
Besides, in the device under review, the checking of each condition of forming modifiable address digits of the memory unit for storing control information is carried out by a separate signal arriving from the analysis signal forming decoders, which accounts for a great number of connections and poor reliability of the device.
Furthermore, in the known device under review, the branching is oriented towards the realization of specific microprograms, and each analysis of conditions affecting address modification of the memory unit for storing control information is related to specific situations which occur in the course of executing said microprograms; as a result, the branching means and, consequently, the storage device itself cannot be used for a different system of instructions.